
package org.springframework.beans.factory.support;

import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import org.springframework.beans.factory.BeanCreationException;
import org.springframework.beans.factory.BeanCreationNotAllowedException;
import org.springframework.beans.factory.BeanCurrentlyInCreationException;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.config.SingletonBeanRegistry;
import org.springframework.core.SimpleAliasRegistry;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Generic registry for shared bean instances, implementing the
 * {@link org.springframework.beans.factory.config.SingletonBeanRegistry}.
 * Allows for registering singleton instances that should be shared
 * for all callers of the registry, to be obtained via bean name.
 *
 * <p>
 * Also supports registration of
 * {@link org.springframework.beans.factory.DisposableBean} instances,
 * (which might or might not correspond to registered singletons),
 * to be destroyed on shutdown of the registry. Dependencies between
 * beans can be registered to enforce an appropriate shutdown order.
 *
 * <p>
 * This class mainly serves as base class for
 * {@link org.springframework.beans.factory.BeanFactory} implementations,
 * factoring out the common management of singleton bean instances. Note that
 * the {@link org.springframework.beans.factory.config.ConfigurableBeanFactory}
 * interface extends the {@link SingletonBeanRegistry} interface.
 *
 * <p>
 * Note that this class assumes neither a bean definition concept
 * nor a specific creation process for bean instances, in contrast to
 * {@link AbstractBeanFactory} and {@link DefaultListableBeanFactory}
 * (which inherit from it). Can alternatively also be used as a nested
 * helper to delegate to.
 *
 * @author Juergen Hoeller
 * @since 2.0
 * @see #registerSingleton
 * @see #registerDisposableBean
 * @see org.springframework.beans.factory.DisposableBean
 * @see org.springframework.beans.factory.config.ConfigurableBeanFactory
 */
public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements SingletonBeanRegistry
{
    
    /** Maximum number of suppressed exceptions to preserve. */
    private static final int SUPPRESSED_EXCEPTIONS_LIMIT = 100;
    
    /** Cache of singleton objects: bean name to bean instance. */
    private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
    
    /** Cache of singleton factories: bean name to ObjectFactory. */
    private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<>(16);
    
    /** Cache of early singleton objects: bean name to bean instance. */
    private final Map<String, Object> earlySingletonObjects = new ConcurrentHashMap<>(16);
    
    /** Set of registered singletons, containing the bean names in registration order. */
    private final Set<String> registeredSingletons = new LinkedHashSet<>(256);
    
    /** Names of beans that are currently in creation. */
    private final Set<String> singletonsCurrentlyInCreation = Collections.newSetFromMap(new ConcurrentHashMap<>(16));
    
    /** Names of beans currently excluded from in creation checks. */
    private final Set<String> inCreationCheckExclusions = Collections.newSetFromMap(new ConcurrentHashMap<>(16));
    
    /** Collection of suppressed Exceptions, available for associating related causes. */
    @Nullable
    private Set<Exception> suppressedExceptions;
    
    /** Flag that indicates whether we're currently within destroySingletons. */
    private boolean singletonsCurrentlyInDestruction = false;
    
    /** Disposable bean instances: bean name to disposable instance. */
    private final Map<String, Object> disposableBeans = new LinkedHashMap<>();
    
    /** Map between containing bean names: bean name to Set of bean names that the bean contains. */
    private final Map<String, Set<String>> containedBeanMap = new ConcurrentHashMap<>(16);
    
    /** Map between dependent bean names: bean name to Set of dependent bean names. */
    private final Map<String, Set<String>> dependentBeanMap = new ConcurrentHashMap<>(64);
    
    /**
     * Map between depending bean names: bean name to Set of bean names for the bean's dependencies.
     */
    private final Map<String, Set<String>> dependenciesForBeanMap = new ConcurrentHashMap<>(64);
    
    @Override
    public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException
    {
        Assert.notNull(beanName, "Bean name must not be null");
        Assert.notNull(singletonObject, "Singleton object must not be null");
        synchronized (this.singletonObjects)
        {
            Object oldObject = this.singletonObjects.get(beanName);
            if(oldObject != null)
            {
                throw new IllegalStateException("Could not register object ["
                        + singletonObject +
                        "] under bean name '" + beanName + "': there is already object [" + oldObject + "] bound");
            }
            addSingleton(beanName, singletonObject);
        }
    }
    
    /**
     * Add the given singleton object to the singleton cache of this factory.
     * <p>
     * To be called for eager registration of singletons.
     * 
     * @param beanName the name of the bean
     * @param singletonObject the singleton object
     */
    protected void addSingleton(String beanName, Object singletonObject)
    {
        synchronized (this.singletonObjects)
        {
            // TODO
            if("refA".equalsIgnoreCase(beanName) || "refB".equalsIgnoreCase(beanName))
            {
                System.out.println("DefaultSingletonBeanRegistry :: 装载成品 " + beanName + "  " + singletonObject);
            }
            this.singletonObjects.put(beanName, singletonObject);
            this.singletonFactories.remove(beanName);
            this.earlySingletonObjects.remove(beanName);
            this.registeredSingletons.add(beanName);
        }
    }
    
    /**
     * Add the given singleton factory for building the specified singleton
     * if necessary.
     * <p>
     * To be called for eager registration of singletons, e.g. to be able to
     * resolve circular references.
     * 
     * @param beanName the name of the bean
     * @param singletonFactory the factory for the singleton object
     */
    protected void addSingletonFactory(String beanName, ObjectFactory<?> singletonFactory)
    {
        Assert.notNull(singletonFactory, "Singleton factory must not be null");
        synchronized (this.singletonObjects)
        {
            if(!this.singletonObjects.containsKey(beanName))
            {
                // TODO
                if("refA".equalsIgnoreCase(beanName) || "refB".equalsIgnoreCase(beanName))
                {
                    System.out.println("DefaultSingletonBeanRegistry :: 装载第三级 对象工厂 " + beanName);
                }
                this.singletonFactories.put(beanName, singletonFactory);
                this.earlySingletonObjects.remove(beanName);
                this.registeredSingletons.add(beanName);
            }
        }
    }
    
    @Override
    @Nullable
    public Object getSingleton(String beanName)
    {
        return getSingleton(beanName, true);
    }
    
    /**
     * Return the (raw) singleton object registered under the given name.
     * <p>
     * Checks already instantiated singletons and also allows for an early
     * reference to a currently created singleton (resolving a circular reference).
     * 
     * @param beanName the name of the bean to look for
     * @param allowEarlyReference whether early references should be created or not
     * @return the registered singleton object, or {@code null} if none found
     */
    @Nullable
    protected Object getSingleton(String beanName, boolean allowEarlyReference)
    {
        // Quick check for existing instance without full singleton lock
        Object singletonObject = this.singletonObjects.get(beanName);
        if(singletonObject == null && isSingletonCurrentlyInCreation(beanName))
        {
            singletonObject = this.earlySingletonObjects.get(beanName);
            if(singletonObject == null && allowEarlyReference)
            {
                synchronized (this.singletonObjects)
                {
                    // Consistent creation of early reference within full singleton lock
                    singletonObject = this.singletonObjects.get(beanName);
                    if(singletonObject == null)
                    {
                        singletonObject = this.earlySingletonObjects.get(beanName);
                        if(singletonObject == null)
                        {
                            ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
                            if(singletonFactory != null)
                            {
                                singletonObject = singletonFactory.getObject();
                                // TODO
                                if("refA".equalsIgnoreCase(beanName) || "refB".equalsIgnoreCase(beanName))
                                {
                                    System.out.println("DefaultSingletonBeanRegistry :: 从第三级缓存对象工厂获取对象，装载半成品  " + beanName + "  " +singletonObject);
                                }
                                this.earlySingletonObjects.put(beanName, singletonObject);
                                this.singletonFactories.remove(beanName);
                            }
                        }
                    }
                }
            }
            else
            {
                // TODO
                if("refA".equalsIgnoreCase(beanName) || "refB".equalsIgnoreCase(beanName))
                {
                    System.out.println("DefaultSingletonBeanRegistry :: 获取半成品 " + beanName + " " +singletonObject);
                }
            }
        }
        else
        { // TODO
            if("refA".equalsIgnoreCase(beanName) || "refB".equalsIgnoreCase(beanName))
            {
//                System.out.println("DefaultSingletonBeanRegistry :: singletonObjects.get not find " + beanName);
            }
        }
        return singletonObject;
    }
    
    /**
     * Return the (raw) singleton object registered under the given name,
     * creating and registering a new one if none registered yet.
     * 
     * @param beanName the name of the bean
     * @param singletonFactory the ObjectFactory to lazily create the singleton
     *            with, if necessary
     * @return the registered singleton object
     */
    public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory)
    {
        Assert.notNull(beanName, "Bean name must not be null");
        synchronized (this.singletonObjects)
        {
            Object singletonObject = this.singletonObjects.get(beanName);
            if(singletonObject == null)
            {
                if(this.singletonsCurrentlyInDestruction)
                {
                    throw new BeanCreationNotAllowedException(beanName,
                            "Singleton bean creation not allowed while singletons of this factory are in destruction "
                                    +
                                    "(Do not request a bean from a BeanFactory in a destroy method implementation!)");
                }
                if(logger.isDebugEnabled())
                {
                    logger.debug("Creating shared instance of singleton bean '" + beanName + "'");
                }
                beforeSingletonCreation(beanName);
                boolean newSingleton = false;
                boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
                if(recordSuppressedExceptions)
                {
                    this.suppressedExceptions = new LinkedHashSet<>();
                }
                try
                {
                    singletonObject = singletonFactory.getObject();
                    newSingleton = true;
                }
                catch (IllegalStateException ex)
                {
                    // Has the singleton object implicitly appeared in the meantime ->
                    // if yes, proceed with it since the exception indicates that state.
                    singletonObject = this.singletonObjects.get(beanName);
                    if(singletonObject == null)
                    {
                        throw ex;
                    }
                }
                catch (BeanCreationException ex)
                {
                    if(recordSuppressedExceptions)
                    {
                        for(Exception suppressedException : this.suppressedExceptions)
                        {
                            ex.addRelatedCause(suppressedException);
                        }
                    }
                    throw ex;
                }
                finally
                {
                    if(recordSuppressedExceptions)
                    {
                        this.suppressedExceptions = null;
                    }
                    afterSingletonCreation(beanName);
                }
                if(newSingleton)
                {
                    addSingleton(beanName, singletonObject);
                }
            }
            return singletonObject;
        }
    }
    
    /**
     * Register an exception that happened to get suppressed during the creation of a
     * singleton bean instance, e.g. a temporary circular reference resolution problem.
     * <p>
     * The default implementation preserves any given exception in this registry's
     * collection of suppressed exceptions, up to a limit of 100 exceptions, adding
     * them as related causes to an eventual top-level {@link BeanCreationException}.
     * 
     * @param ex the Exception to register
     * @see BeanCreationException#getRelatedCauses()
     */
    protected void onSuppressedException(Exception ex)
    {
        synchronized (this.singletonObjects)
        {
            if(this.suppressedExceptions != null && this.suppressedExceptions.size() < SUPPRESSED_EXCEPTIONS_LIMIT)
            {
                this.suppressedExceptions.add(ex);
            }
        }
    }
    
    /**
     * Remove the bean with the given name from the singleton cache of this factory,
     * to be able to clean up eager registration of a singleton if creation failed.
     * 
     * @param beanName the name of the bean
     * @see #getSingletonMutex()
     */
    protected void removeSingleton(String beanName)
    {
        synchronized (this.singletonObjects)
        {
            this.singletonObjects.remove(beanName);
            this.singletonFactories.remove(beanName);
            this.earlySingletonObjects.remove(beanName);
            this.registeredSingletons.remove(beanName);
        }
    }
    
    @Override
    public boolean containsSingleton(String beanName)
    {
        return this.singletonObjects.containsKey(beanName);
    }
    
    @Override
    public String[] getSingletonNames()
    {
        synchronized (this.singletonObjects)
        {
            return StringUtils.toStringArray(this.registeredSingletons);
        }
    }
    
    @Override
    public int getSingletonCount()
    {
        synchronized (this.singletonObjects)
        {
            return this.registeredSingletons.size();
        }
    }
    
    public void setCurrentlyInCreation(String beanName, boolean inCreation)
    {
        Assert.notNull(beanName, "Bean name must not be null");
        if(!inCreation)
        {
            this.inCreationCheckExclusions.add(beanName);
        }
        else
        {
            this.inCreationCheckExclusions.remove(beanName);
        }
    }
    
    public boolean isCurrentlyInCreation(String beanName)
    {
        Assert.notNull(beanName, "Bean name must not be null");
        return (!this.inCreationCheckExclusions.contains(beanName) && isActuallyInCreation(beanName));
    }
    
    protected boolean isActuallyInCreation(String beanName)
    {
        return isSingletonCurrentlyInCreation(beanName);
    }
    
    /**
     * Return whether the specified singleton bean is currently in creation
     * (within the entire factory).
     * 
     * @param beanName the name of the bean
     */
    public boolean isSingletonCurrentlyInCreation(String beanName)
    {
        return this.singletonsCurrentlyInCreation.contains(beanName);
    }
    
    /**
     * Callback before singleton creation.
     * <p>
     * The default implementation register the singleton as currently in creation.
     * 
     * @param beanName the name of the singleton about to be created
     * @see #isSingletonCurrentlyInCreation
     */
    protected void beforeSingletonCreation(String beanName)
    {
        if(!this.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.add(beanName))
        {
            throw new BeanCurrentlyInCreationException(beanName);
        }
    }
    
    /**
     * Callback after singleton creation.
     * <p>
     * The default implementation marks the singleton as not in creation anymore.
     * 
     * @param beanName the name of the singleton that has been created
     * @see #isSingletonCurrentlyInCreation
     */
    protected void afterSingletonCreation(String beanName)
    {
        if(!this.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.remove(beanName))
        {
            throw new IllegalStateException("Singleton '" + beanName + "' isn't currently in creation");
        }
    }
    
    /**
     * Add the given bean to the list of disposable beans in this registry.
     * <p>
     * Disposable beans usually correspond to registered singletons,
     * matching the bean name but potentially being a different instance
     * (for example, a DisposableBean adapter for a singleton that does not
     * naturally implement Spring's DisposableBean interface).
     * 
     * @param beanName the name of the bean
     * @param bean the bean instance
     */
    public void registerDisposableBean(String beanName, DisposableBean bean)
    {
        synchronized (this.disposableBeans)
        {
            this.disposableBeans.put(beanName, bean);
        }
    }
    
    /**
     * Register a containment relationship between two beans,
     * e.g. between an inner bean and its containing outer bean.
     * <p>
     * Also registers the containing bean as dependent on the contained bean
     * in terms of destruction order.
     * 
     * @param containedBeanName the name of the contained (inner) bean
     * @param containingBeanName the name of the containing (outer) bean
     * @see #registerDependentBean
     */
    public void registerContainedBean(String containedBeanName, String containingBeanName)
    {
        synchronized (this.containedBeanMap)
        {
            Set<String> containedBeans = this.containedBeanMap.computeIfAbsent(containingBeanName, k -> new LinkedHashSet<>(8));
            if(!containedBeans.add(containedBeanName))
            {
                return;
            }
        }
        registerDependentBean(containedBeanName, containingBeanName);
    }
    
    /**
     * Register a dependent bean for the given bean,
     * to be destroyed before the given bean is destroyed.
     * 
     * @param beanName the name of the bean
     * @param dependentBeanName the name of the dependent bean
     */
    public void registerDependentBean(String beanName, String dependentBeanName)
    {
        String canonicalName = canonicalName(beanName);
        
        synchronized (this.dependentBeanMap)
        {
            Set<String> dependentBeans = this.dependentBeanMap.computeIfAbsent(canonicalName, k -> new LinkedHashSet<>(8));
            if(!dependentBeans.add(dependentBeanName))
            {
                return;
            }
        }
        
        synchronized (this.dependenciesForBeanMap)
        {
            Set<String> dependenciesForBean = this.dependenciesForBeanMap.computeIfAbsent(dependentBeanName,
                    k -> new LinkedHashSet<>(8));
            dependenciesForBean.add(canonicalName);
        }
    }
    
    /**
     * Determine whether the specified dependent bean has been registered as
     * dependent on the given bean or on any of its transitive dependencies.
     * 
     * @param beanName the name of the bean to check
     * @param dependentBeanName the name of the dependent bean
     * @since 4.0
     */
    protected boolean isDependent(String beanName, String dependentBeanName)
    {
        synchronized (this.dependentBeanMap)
        {
            return isDependent(beanName, dependentBeanName, null);
        }
    }
    
    private boolean isDependent(String beanName, String dependentBeanName, @Nullable Set<String> alreadySeen)
    {
        if(alreadySeen != null && alreadySeen.contains(beanName))
        {
            return false;
        }
        String canonicalName = canonicalName(beanName);
        Set<String> dependentBeans = this.dependentBeanMap.get(canonicalName);
        if(dependentBeans == null)
        {
            return false;
        }
        if(dependentBeans.contains(dependentBeanName))
        {
            return true;
        }
        for(String transitiveDependency : dependentBeans)
        {
            if(alreadySeen == null)
            {
                alreadySeen = new HashSet<>();
            }
            alreadySeen.add(beanName);
            if(isDependent(transitiveDependency, dependentBeanName, alreadySeen))
            {
                return true;
            }
        }
        return false;
    }
    
    /**
     * Determine whether a dependent bean has been registered for the given name.
     * 
     * @param beanName the name of the bean to check
     */
    protected boolean hasDependentBean(String beanName)
    {
        return this.dependentBeanMap.containsKey(beanName);
    }
    
    /**
     * Return the names of all beans which depend on the specified bean, if any.
     * 
     * @param beanName the name of the bean
     * @return the array of dependent bean names, or an empty array if none
     */
    public String[] getDependentBeans(String beanName)
    {
        Set<String> dependentBeans = this.dependentBeanMap.get(beanName);
        if(dependentBeans == null)
        {
            return new String[0];
        }
        synchronized (this.dependentBeanMap)
        {
            return StringUtils.toStringArray(dependentBeans);
        }
    }
    
    /**
     * Return the names of all beans that the specified bean depends on, if any.
     * 
     * @param beanName the name of the bean
     * @return the array of names of beans which the bean depends on,
     *         or an empty array if none
     */
    public String[] getDependenciesForBean(String beanName)
    {
        Set<String> dependenciesForBean = this.dependenciesForBeanMap.get(beanName);
        if(dependenciesForBean == null)
        {
            return new String[0];
        }
        synchronized (this.dependenciesForBeanMap)
        {
            return StringUtils.toStringArray(dependenciesForBean);
        }
    }
    
    public void destroySingletons()
    {
        if(logger.isTraceEnabled())
        {
            logger.trace("Destroying singletons in " + this);
        }
        synchronized (this.singletonObjects)
        {
            this.singletonsCurrentlyInDestruction = true;
        }
        
        String[] disposableBeanNames;
        synchronized (this.disposableBeans)
        {
            disposableBeanNames = StringUtils.toStringArray(this.disposableBeans.keySet());
        }
        for(int i = disposableBeanNames.length - 1; i >= 0; i--)
        {
            destroySingleton(disposableBeanNames[i]);
        }
        
        this.containedBeanMap.clear();
        this.dependentBeanMap.clear();
        this.dependenciesForBeanMap.clear();
        
        clearSingletonCache();
    }
    
    /**
     * Clear all cached singleton instances in this registry.
     * 
     * @since 4.3.15
     */
    protected void clearSingletonCache()
    {
        synchronized (this.singletonObjects)
        {
            this.singletonObjects.clear();
            this.singletonFactories.clear();
            this.earlySingletonObjects.clear();
            this.registeredSingletons.clear();
            this.singletonsCurrentlyInDestruction = false;
        }
    }
    
    /**
     * Destroy the given bean. Delegates to {@code destroyBean}
     * if a corresponding disposable bean instance is found.
     * 
     * @param beanName the name of the bean
     * @see #destroyBean
     */
    public void destroySingleton(String beanName)
    {
        // Remove a registered singleton of the given name, if any.
        removeSingleton(beanName);
        
        // Destroy the corresponding DisposableBean instance.
        DisposableBean disposableBean;
        synchronized (this.disposableBeans)
        {
            disposableBean = (DisposableBean) this.disposableBeans.remove(beanName);
        }
        destroyBean(beanName, disposableBean);
    }
    
    /**
     * Destroy the given bean. Must destroy beans that depend on the given
     * bean before the bean itself. Should not throw any exceptions.
     * 
     * @param beanName the name of the bean
     * @param bean the bean instance to destroy
     */
    protected void destroyBean(String beanName, @Nullable DisposableBean bean)
    {
        // Trigger destruction of dependent beans first...
        Set<String> dependencies;
        synchronized (this.dependentBeanMap)
        {
            // Within full synchronization in order to guarantee a disconnected Set
            dependencies = this.dependentBeanMap.remove(beanName);
        }
        if(dependencies != null)
        {
            if(logger.isTraceEnabled())
            {
                logger.trace("Retrieved dependent beans for bean '" + beanName + "': " + dependencies);
            }
            for(String dependentBeanName : dependencies)
            {
                destroySingleton(dependentBeanName);
            }
        }
        
        // Actually destroy the bean now...
        if(bean != null)
        {
            try
            {
                bean.destroy();
            }
            catch (Throwable ex)
            {
                if(logger.isWarnEnabled())
                {
                    logger.warn("Destruction of bean with name '" + beanName + "' threw an exception", ex);
                }
            }
        }
        
        // Trigger destruction of contained beans...
        Set<String> containedBeans;
        synchronized (this.containedBeanMap)
        {
            // Within full synchronization in order to guarantee a disconnected Set
            containedBeans = this.containedBeanMap.remove(beanName);
        }
        if(containedBeans != null)
        {
            for(String containedBeanName : containedBeans)
            {
                destroySingleton(containedBeanName);
            }
        }
        
        // Remove destroyed bean from other beans' dependencies.
        synchronized (this.dependentBeanMap)
        {
            for(Iterator<Map.Entry<String, Set<String>>> it = this.dependentBeanMap.entrySet().iterator(); it.hasNext();)
            {
                Map.Entry<String, Set<String>> entry = it.next();
                Set<String> dependenciesToClean = entry.getValue();
                dependenciesToClean.remove(beanName);
                if(dependenciesToClean.isEmpty())
                {
                    it.remove();
                }
            }
        }
        
        // Remove destroyed bean's prepared dependency information.
        this.dependenciesForBeanMap.remove(beanName);
    }
    
    /**
     * Exposes the singleton mutex to subclasses and external collaborators.
     * <p>
     * Subclasses should synchronize on the given Object if they perform
     * any sort of extended singleton creation phase. In particular, subclasses
     * should <i>not</i> have their own mutexes involved in singleton creation,
     * to avoid the potential for deadlocks in lazy-init situations.
     */
    @Override
    public final Object getSingletonMutex()
    {
        return this.singletonObjects;
    }
    
}
